Field of Invention
The present invention is in the field of organic and natural product chemistry. The present invention relates to an efficient process for purification, simultaneous extraction, and separation of monohydroxycarotenoids from dihydroxycarotenoids in various natural products or in synthetic mixtures. Similarly, the process can also be applied to the simultaneous extraction, saponification, and separation of esterified mono- and dihydroxycarotenoids in natural products and their oleoresins or in their synthetic mixtures. Therefore, esterified and unesterified monohydroxycarotenoids such as (3R)-β-cryptoxanthin and (3R,6′R)-α-cryptoxanthin can be efficiently separated from their corresponding dihydroxycarotenoids such as (3R,3′R,6′R)-lutein and (3R,3′R)-zeaxanthin that are found in various plants or in synthetic mixtures.
Background Art
(3R)-β-Cryptoxanthin, (3R,6′R)-α-cryptoxanthin, (3R,3′R,6′R)-lutein, and (3R,3′R)-zeaxanthin are among the 12 major dietary carotenoids which are found in human serum, milk, major organs, and tissues. In view of the biological activity of carotenoids in the prevention of chronic diseases such as cancer, age-related macular degeneration, and cardiovascular disease, industrial production of a wide range of purified carotenoids is of great importance. Numerous processes have been reported for the extraction and isolation of these carotenoids from plants and synthetic mixtures. However, according to all of these processes the purified carotenoid product consists of a mixture of mono- and dihydroxycarotenoids in varying compositions. Therefore, to this date there is no reported process that allows for the simultaneous extraction, saponification, separation, and purification of these carotenoids from plants or synthetic mixtures. In most cases, these carotenoids are present in plants and natural products in their esterified forms with fatty acids such as myristic and palmitic acids. The chemical structures of monohydroxycarotenoids, (3R)-β-cryptoxanthin and (3R,6′R)-α-cryptoxanthin, and dihydroxycarotenoids, (3R,3′R,6′R)-lutein and (3R,3′R)-zeaxanthin, are shown in FIG. 1. The chemical structure of mono- and diacetates of these carotenoids that are typically prepared by partial synthesis from these carotenoids are also shown in FIG. 1.
Numerous processes have been reported in which plants are first extracted to obtain an oleoresin that is subsequently saponified to yield the unesterified form of these carotenoids. The unesterified forms of these carotenoids are then subjected to crystallization and purification for use as nutritional supplements. However, these purified carotenoids consist of varying compositions of mono- and dihydroxycarotenoids. For example, plants that are predominantly rich in (3R,3′R,6′R)-lutein also have minor quantities of (3R,6′R)-α-cryptoxanthin and plants that are abundant in (3R,3′R)-zeaxanthin contain minor levels of (3R)-β-cryptoxanthin.
Because mono- and dihydroxycarotenoids exhibit different biological activities with regard to their nutritional benefits, the separation of each of these individual carotenoids is of great importance. The present invention describes efficient processes for the purification, simultaneous extraction, and saponification, as well as for the separation of monohydroxycarotenoids from dihydroxycarotenoids.